Piston for pressure producing devices



Aug. 9, 1938.. M. w. BOWEN PISTON FOR PRESSURE PRODUCING DEVICES Filed Feb. 27, 1956 INVENTOR. MVea/v W0 WEN BY 7775M 5 m w v I Patented Aug. 9,

UNIT-ED. STATES-V",

PATENT OFFICE PISTON FOB PRESSURE PRODUCING DEVICES Myron W. Bowen, Detroit, Mich, assignor to Bydraulic, Brake Company, Detroit, Mich, a corporation of California Application February 27, 1936, Serial No. 65,916

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This invention relates to fluid pressure producing devices.- and more particularly to pistons for such devices. a

Broadly the invention .comprehends a fluid v pressure producing device including a cylinder,

a piston reciprocable therein, a flexible cup on the head of the piston, and means i'orsavingthe cup from injury.

An objector the invention is to provide a piston jg carrying a flexible cup. with a shell for the protection of the cup. a Another object of the invention is to'provide a piston having a flexible cup on its head, with a; protective shell'movable relative to the'piston and the cup. a

Another object of the invention'is'to provide acylinder, 9. piston reciprocable therein, aflexible cup on the head; ofthe piston, and a'movable shell intermediate the head of the piston and cup' and the wall of the cylinder.

Afurther object of the invention is to provide a cylinder, a .piston reciprocable therein having on itshead a leak-proof cup andv a protective shell reciprocable between the head of the piston a 2 and the. cylinder embracing the cup and operative to uncover a portion of the cup on the compression stroke of the piston and to completely 1 telescope the cup when the piston'is fully re- .tracted. Other objects of the invention will appear from the following description taken in connection with the drawingzwhiel'r form's apart of this spccifl cation. and in which,-

Fig. 1 is .a schematicviewof a fluid pressure braking system embodying the invention; c

I Fig. 2 is a vertical longitudinal sectional view of the fluid pressure producing device;

' Fig. 3 is a fragmentary view, in section. illus- .t'rating the piston on its compression stroke: 0 Fig. 4 is anenlarged fragmentary view illustrating the relation 01' the shift'able shell to the flexible cup when the piston isE in fully retracted position; and

- Fig. .5 is an enlarged fragmentary view i1lus-. trating'the relation or the shiftable shell and the flexible cup when the piston is on its compression 1 stroke. 3 1

Referring to the drawing for more specific details of the invention, ill represents a fluid reservoir of conventional type having at its base a cylinder ii. The cylinder is provided with a port ll communicating with the reservoir,-and a head il having an axial bore providing a discharge port II for the cylinder. the port being controlled 1 by a two-way valve 20. 1

v wheels of the vehicle;

(Cl. Gil-64.6)

A fluid pressure delivery pipe or conduit 2 2 suitably connected to the head in direct communication with the discharge. port it has branches 24, 26, 28 and 30 connected respectively to fluid pressure actuatedmotors 32. The motors are preferably arranged in pairs, one pair for actuating the friction elements of brakes associated with the front wheels, of the vehicle, and another pair for actuating brakesjassociated with the rear As shown,'the brakes are of conventional type including a fixed support orv backing plate 34, a rotatable drum associated therewith, a pair of corresponding interchangeable friction elements or shoes 38 pivoted on the backingplate, and a 1g in conjunction. with" the wall of the cylinder an annular chamber 52. The skirt of the piston carries a leak-proof washer 54 providing against 7 seepage of fluid past the piston, and the head of the piston has a'plurality of spaced ports 56 3 providing communications between the annular chamber 52 and that portion of the cylinder forward oi the' piston. -A leak-proof cup 58 is seated on theheadof the piston. andga spring 60 interposed between the cup 58 and the two-way 5 valve serves to retain these elements against displacement and also to return the piston to its retracted position.

The head It of the piston has on its back a I concentric sleeve '62 telescoping a portion-of the 40 reduced section 50 of the piston, and the outer wall of this; sleeve has a double diameter. the two 'diametersproviding' at their junction an annular Shoulder N. A ish'ellltfltted in the cylinder 12 with small' clearance ispositioned 45 intermediate the piston and the wall of the cylinder and is reciprocable relative to the cylinder and piston.

' The forward end of the'shell'tt a inner wall it embracing the cup 58. Asyshown, 50

the shell has a double diameter. providing at the a junction of the'two diameters an annular shoulder n adaptable for cooperation with the annular shoulder 'oif'the-sleeve "to limit the I movement of the shell in one direction. The BIL f" shoulder 18 seats on a stop 12 when the piston is in fully retracted position, and the shoulder 18 is provided with a plurality of spaced openings I4 preferably registering with the ports 58 in the head or the piston so as to provide for the free passage of fluid from the annular chamber 52 to the ports. 4

The rear end of that portion of the shlell'ha'ving the smaller diameter has a flange I8 extending inwardly beyond the free end of the sleeve 7 82, and a spring I8 sleeved on the reduced section 58 intermediate the back of the piston headand the flange 18 urges the shell toward an annular seat 88 when the piston is moved on its compression stroke. A recess 82 in the back of the piston receives one end of a thrust pin 88, the other end of which may be connected as by a rod 88 to a foot pedal lever 88 pivoted on a suitable support 88 and connected by a retractile spring 82 to a fixed support 88.

In operation, 'upon depressing the foot pedal lever 88 force is transmitted therefrom through the rod 88 and thrust pin 88 to the piston 82 resulting in moving the piston on its compression stroke. Duringthe initial movement of the piston on its compression stroke the spring 18 retains the shell 88 against the stop 12, and as the piston advances the collapsible leak-proof cup 58 is moved from its position within the shell suiticientiy forward of the shell to engage the major portion of its flange or lip with the wall of the motors 82, causing actuation of the motors with the resultant movement of the shoes 88 against the resistance of the springs 88 into engagement with the drums 88.

Upon release of the applied force, the piston 42 is returned to its retracted position under the influence of the spring 88. As the piston returns to its retracted position, a partial vacuum' is created in the cylinder forward ofthe piston resulting in drawing fluid from the reservoir through the port it into the annular chamber 52, thence through the openings 18 in the shell 88 and the ports 58 in the head of the piston past the cup 58 into that portion of the cylinder forward of the piston. As the piston returns to its retracted position, the shell 88 engages the stop I2, and as the piston moves to its fully retracted position the collapsible leak-proof cup 58 is telescoped by the shell 88. During this operation fluid is returning to the cylinder i2 from the fluid pressure actuated motors 82 under the influence of retractile springs 88 connecting the respective pairs of shoes 88. Hence, the quantity of fluid received by the cylinder may be in excess of the quantity required to completely flll the cylinder. Under this condition, any excess fluid is returned to the reservoir by way oi the clearance between the shell 88 and the wall of the cylinder'and the port i8.

Although this invention has been described in connection with certain specific embodiments, the principles involved are susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

der or to permitby-passing of fluid therebetween,

and a shell arranged intermediate the piston and the cylinder and movable relative to the piston and cylinder to control bypassing of said piston. 3. A fluid pressure producing device comprising a cylinder, a piston reciprocable therein and having a part adapted to form a fluid-tight :seal therewith, a shell arranged intermediate-the piston and cylinder'to control said seal, means retaining the shell against ,movement relative to the cylinder during the initial movement of the piston on its compression stroke, and means for moving the shell and the piston in unison upon further advance of the piston on-its compression stroke. v

4. A fluid pressure producing device comprising a cylinder, a piston reciprocable therein and have ing a part adapted to form a seal therewith, a shell fitted in the cylinder with small clearance intermediate the piston and cylinder, said shell being adapted to control said seal, means retaining the shell against movement relative to the cylinder during the initial movement of the piston on its compression stroke, means for moving the shell and piston in unison as the piston proceeds on its compression stroke, means tor returning the piston to its retracted position, and means i.'or arresting the shell before the piston returns to its fully retracted position. t t 5. A fluid pressure producing device comprising a cylinder, a piston reciprocable therein, a flex ible cup on the head of the piston,'said cup being adapted to form a fluid tight seal between said piston and cylinder, and a shell for controlling said seal, said shell being intermediate the piston and cylinder movable relative to the piston and cylinder and embracing the cup. 8. A fluid pressure producing device comprise ing a cylinder, a piston movable therein, a flexible sealing cup on the head' of the piston, and a 'shell surrounding the piston and cup and movable rela' 'tive thereto to control the sealing action of said cup. I 7. A fluid pressure producing device comprising a cylinder, a piston reciprocable therein, a flexible cup on the head of the piston, said cup being adapted to make a seal with said cylinder, means for advancing the piston, means for returning the piston, and a movable shell arranged intermediate the piston and the cylinder and embracing-the cup and adapted to successively completely tele; scope the cup to break'the seal between said cup and cylinder. 1

8. A fluid pressure'producing device comprising a reservoir, a cylinder supplied therefrom, a piston reciprocable in the cylinder, a flexible cup on the head of the piston, said cup being adapted to forma fluid tight seal, means for advancing the piston, means for returning the piston, and a movable shell interposed between the piston and the cylinder and adapted'to completely telescope the cup when the piston is moved to its fully rea fluid tight seal, means for advancing the piston,

traeted position whereby said seal is broken.

9. A fluid pressure braking system comprising a. pressure producing device including a reservoir, a. cylinder supplied therefrom, fluid pressure actuated motors connected to the cylinder, a. piston reciprocable in the cylinder, 9. flexible cup on the head of the piston, said cupbeing adapted to form 1 means for returning the piston, and a movable shell interposed between the piston and the cylinder adapted to completely telescope the cup when the piston is moved to its fully retracted position 5 whereby said seal is broken.

MYRON w. BOWEN. 

